I thought 'oh, is this a new book'? Then I looked at the date. It seems as though all 'classical' sources on lisp or functional paradigm are either two decades

I thought 'oh, is this a new book'? Then I looked at the date. It seems as though all 'classical' sources on lisp or functional paradigm are either two decades old, or just-out-yesteryear. What happened in between?